Nonstoichiometric Salt Intercalation as a Means to Stabilize Alkali Doping of 2D Materials

Yuanxi Wang, Vincent H. Crespi, Marvin L. Cohen, and Amir Nourhani

Phys. Rev. Lett. 129, 266401 – Published 23 December 2022

Abstract

Although doping with alkali atoms is a powerful technique for introducing charge carriers into physical systems, the resulting charge-transfer systems are generally not air stable. Here we describe computationally a strategy towards increasing the stability of alkali-doped materials that employs stoichiometrically unbalanced salt crystals with excess cations (which could be deposited during, e.g., in situ gating) to achieve doping levels similar to those attained by pure alkali metal doping. The crystalline interior of the salt crystal acts as a template to stabilize the excess dopant atoms against oxidation and deintercalation, which otherwise would be highly favorable. We characterize this doping method for graphene, ${NbSe}_{2}$ , and ${Bi}_{2} {Se}_{3}$ and its effect on direct-to-indirect band gap transitions, 2D superconductivity, and thermoelectric performance. Salt intercalation should be generally applicable to systems which can accommodate this “ionic crystal” doping (and particularly favorable when geometrical packing constraints favor nonstoichiometry).

Received 1 March 2021
Revised 11 August 2022
Accepted 30 September 2022

DOI:https://doi.org/10.1103/PhysRevLett.129.266401

Physics Subject Headings (PhySH)

Dopants Electronic structure

2-dimensional systems Graphene

Density functional calculations

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Yuanxi Wang^1,2, Vincent H. Crespi^1,3, Marvin L. Cohen^4,5, and Amir Nourhani ^6,7,8,*

¹2-Dimensional Crystal Consortium, Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
²Department of Physics, University of North Texas, Denton, Texas 76201, USA
³Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
⁴Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA
⁵Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
⁶Department of Mechanical Engineering, University of Akron, Akron, Ohio 44325, USA
⁷Biomimicry Research and Innovation Center, University of Akron, Akron, Ohio 44325, USA
⁸Departments of Biology, Mathematics, and Chemical, Biomolecular, and Corrosion Engineering, University of Akron, Akron, Ohio 44325, USA